Charge forming device



p 8; 1945. H. w. SMITH Er AL 2,385,112

CHARGE FbRMING DEVICE Filed Aug. 23, 1943 2 Sheets-Sheet l SUCTION BELOW ENGINE CARE-W146. N u: 4:. u m \1 FUEL FLOW=,O.64XH!K FLDW-LBS/HR.

INVENTOR.

Patented Sept. 18, 1945 CHARGE FORMING DEVICE Harold W. Smith and Donald D. Paxton, Los Angeles, Calif., assignors to American Liquid Gas Corporation, Los Angeles, Calif., a corporation of California Application August 23, 1943, Serial No. 499,680

9 Claims. (01. 123-119) This invention relates to means for producing fuel carburetion.

In the operation of internal combustion engines, and particularly airplane engines for military purposes, it has been found that the consumption of liquid fuel during the period of starting an engine is excessively high, and that it causes an engine to operate inefficiently. This is particularly true when the engines are operated under low temperature climatic conditions, for in such cases there is difficulty in starting the engine and properly warming it up for combat flight. In fact, it is often necessary to supply auxiliary heaters to heat the engineand its associated parts for, one or twohours before attempting to start the engine under its own power. In connection with these operations it has been found desirable to supplement or substitute the usual liquid fuel supply with fuel having the characteristics of propane and butane, which are gaseous at normal temperature, since this type of fuel will operate rapidly and efficiently in starting an engine and getting it under conditions of flight. However, it has been found that when fuels of this type are used their physical state is not constant, for under some circumstances the fuel will be in its liquid state and under other circumstances in its vapor state. It is therefore desirable to maintain the fuel in a constant state for carburetion and to insure that the fuel volume increases in a substantially direct ratio to the increase in airflow into the engine as induced by engine suction. It is the principal object of the present invention, therefore, to provide a method and means of carburetion espe-- cially adapted for supplying auxiliary carburetion to engines operating at idling speeds, and which method is characterized by automatically regulating the inflow of fuel to the fuel suction line of the engine in a manner to insure that upon initial operation of the engine adequate fuel supply will be provided for starting purposes, regardless of whether or not the fuel is in a complete gaseous state, is partly gasified, or delivered to the carburetor in a liquid state, and that as the idling speed accelerates the volume of fuel flowing to the engine intake line will increase in direct proportion to the suction.

The present invention contemplates the provision of an auxiliary carburetor structure preferably interposed between the fuel supply and the supercharger of an internal combustion engine, and which carburetor structure is designed to respond to engine suction in a manner to supply an initial priming charge to the engine when starting, and to thereafter automatically increase the fuel supply volume in direct response to increase of engine suction.

- The invention is illustrated by way of example in the accompanying drawings in which:

Figure 1 is a view indicating a schematic arrangement of the auxiliary carburetor with relation to an airplane engine of the radial type.

Fig. 2 is a view showing a plotted graph to indicate the increase in air and fuel flow with relation to the increase in engine suction.

Fig. 3 is a view in central vertical section through the auxiliary carburetor with which the present invention is particularly concerned.

Referring more particularly to the drawings, ill indicates an engine fitted with a supercharger l I. The supercharger II is formed with a suitable connection l2 leading to the usual air inlet 13. Connected to the member [2 at a point between the air inlet I3 and the supercharger I l is a fuel supply pipe M. This is attached to the carburetor unit 15 with which the present invention is concerned. The carburetor unit has a bowl 16 formed with a radial opening H in its side to receive the fuel supply pipe l4. At the center of the bowl I6 is a valve chamber 18. The valve chamber is at right angles to the radial opening I! and is formed with threaded openings l9 and 2|] at its opposite ends. These openings are vertically aligned. The upper opening receives a threaded valve seat structure-2| and the lower opening receives a threaded valve seat structure 22. A valve element 23 is disposed within the chamber l8 and moves upwardly against the valve seat 2 I. As will be hereinafter explained it is normally in its closed position. A valve element 24 is disposed within the chamber I8 and moves downwardly onto the valve seat 22. This valve is normally disposed in its opened position. It will be seen that chamber l8 communicates with the passageway I1, and that outflow of fluid may pass through either of the valve seats 2| or 22 when their valves are opened. The passageway through valve seat 2| communicates with a diaphragm chamber 25 which is closed by a diaphragm 26. stem 21 of the valve 23 at its center and is secured over the upper end of the bowl l6 by a ring 28. The ring 28 is formed with a central passageway of two different diameters, the smaller diameter agreeing with the diameter of the diaphragm chamber 25 and the larger diameter agreeing with that of a pressure space 29, which is formed by a cover plate 30. The plate 30 engages the marginal edge of an upper diaphragm 3|. The dia- The diaphragm 26 is fixed to the phragms 26 and 3| define an intermediate pressure space 32. Attention is directed to the fact, however, that the upper diaphragm 3| is of larger area than the lower diaphragm 26, and that thus a difierential action will be obtained as hereinafter explained. A spacer 33 is disposed between the centers of the two diaphragms and is formed with an upwardly projecting threaded portion 34 which extends into a threaded opening in a rod 35. The upper end of the rod 35 is threaded at 36 to receive a nut 31 and to hold a disc 38. Interposed between the disc 38 and the upper face of the plate 36 is a spring 39 which tends to hold the diaphragms 26 and 3i upwardly and to hold the valve 23 on its seat. A cylindrical housing 40 is formed integral with the plate 30 and circumscribes the spring 39. The rod 35 when extending through the plate 30 has a free fit with the walls of opening 4| so that atmospheric air pressure will act upon the upper face of the dia- Phraem 3 As here shown, the carburetor bowl I6 is formed with a radially disposed outlet opening 42. This is threaded and receives the end of pipe l4 connected with the suction side of the supercharger H. At the inner end of the radial passageway 42 is a duct 3 which communicates with the space 32 between the diaphragms 23 and 3|. At the inner end of the passageway 42 there is also a duct -34 which communicates with the chamber 25 occurring beneath diaphragm 26.

The valve 2Q is fitted with a stem 55 which extends downwardly through the valve seat structure 22 and is formed with a threaded portion 56 receiving a nut 47. This threaded portion extends through the center of a diaphragm 48. The margin of this diaphragm is held against the lower face of the bowl It by the upper face of a housing #39. The housing 49 is substantially cylindrical and is formed intermediate its ends with an inwardly extending annular partition flange 53 which receives a valve cylinder The valve cylinder 5! extends downwardly below the flange 53. Its lower end is closed by a cylinder head 52-. The valve cylinder is formed with a partition 53 intermediate its ends. The partition has a central opening 5 1 through it. The upper face of the partition wall 53 surrounding the opening 54 is formed with a valve seat 55 upon which a valve 516 may rest. Disposed between t e valve 56 and the central rigid portion of the diaphragm 48 is aspring 59. This tends to separate the valve and the diaphragm and to urge the diaphragm upwardly to a position against'stop fingers 6i] while urging the valve down onto its seat. The valve 56 is formed with a stem 6! which extends downwardly through the opening 54 and terminates in an enlarged disc 62. The disc 62 has upwardly extending stop fingers 63. which limit the upward movement of the valve. Disposed beneath the disc 62 and between it. and the cylinder head 52 is a bellows 64', here shown as of the Sylphon type. This bellows is sealed at its opposite ends and is partially filled with the same type of fuel which is to. be passed through the carburetor, such for example as propane. When stating that the bellows. is. partially filled with this fuel it is to be understoodv that the bellows is partially filled with liquid propane, and that during functioning of the. carburetor the propane may change from liquid to, gaseous state in varying degrees. The bellows 6.4 subjected to external pressure produced by fuel passing through ducts B5 in the side wall of the cylinder 51 and communicating with a cylindrical bore 66 of the housing 49. The

fuel entering the bore 66 is conducted from the induction line l4 through a duct 6'! in the bowl 5 to a duct 68 in the housing 49.

The lower end of the housing 49 is formed with a flange 69 against which a head 10 is secured by cap screws H. This head closes the lower end of the bore 66 and is formed with an upwardly projecting annular flange 12 against which a valve cup 13 normally rests. The cup has a lower disc-shaped portion 14 resting directly on the flange 12 and is formed with a central passageway '15 and a plurality of other passageways "it which are arranged circumferentially around the central passageway and are separate therefrom. A cylindrical wall section 57 extends upwardly from the disc portion 7 3 and provides a seat for a spring 78 which is disposed between the cup 13 and the transverse partition wall 50 of the housing 49. This tends to urge the cup toits lowermost position as limited by the annular flange 12.

1 Formed centrally of the head 10 is a threaded bore 19 which receives a valve seat 89. This valve seat is formed with a central opening 8| through which a valve stemti extends. This stem carries a valve 83 at its upper end and a valve 84 at its lower end. The valves are spaced from each other so that when they move to their alternate positions the passageway 81 will be closed. .A disc is associated with the valve 83* so that when it moves upwardly to engage the portion 1 3 of the cup 73 the upward movement ofthe valve structure will be limited. A rod 8% extends upwardly from the disc and into a spring cupS'l carried by the cylinder head 52. A spring 83is disposed. within the cup and around the rod and rests against the upper face of the portion 85 of thevalve. This spring tends to urgethevalve 83 downwardly against the seat 80, and thus normally closes the passageway Bl. The lower end of the valve stem 82 is connected to a diaphragm 89 which is disposed between the member ill and a cover plate 90. The cover plate Qilfis formed with a port 9| communicating with the. atmosphere and delivering atmospherict air into space 92 which. occurs between the cover plates!) and the diaphragm 89. A space 93 occurs between the diaphragm 89 and themember 76'. This space communicates with the suction side of the carburetor through a priming. passageway 94. The suction pipe i l also communicates with a, space 95 through a duct 96. The space'95- is defined between the diaphragm 48- and the lower face 91 of the bowl IS. A relatively small duct 98 establishes communication between the priming passageway 94 and a space 99 which occurs between the diaphragm .453 and the partition wall 50 of the housing lfl.

Theducts 44 and 96- are' fitted at points intermediate thei-r-end's with restricted orifice plates 4G0 and I0],- respectively. These together with the restricted-orifice 98 tend to insure that there notbe an undesirable pressure drop when engine suction increases,'and that the fuel entering'thexsuction pipe MI will be maintained at a constant increase in volume with relation to the increase in engine. suction.

In operation of the carburetor with which the present invention is concerned it is to be understood that it is connected through the suction pipe Mto the conduit l2 leading from the member [3 to the supercharger H. Under these circumstances the fuel delivered from a source of supply through the induction pipe l4 .hasa definitepressure. For the purposes of the present explanation it will be assumed that the fuel is propane and that the operating pressure is fifteen pounds gauge. This pressure is constantly imposed upon the various fluid responsive elements of the carburetor. At this time the valve 24 is held open by the spring 59 so that the fuel may pass downwardly through the valve seat, 28 and into the chamber 95. At the same time fuel passes downwardly through the ducts B1 and 68 into the chamber 66 and from thence through the ports 65 into the valve cylinder. 5| where it acts against the bellows 64. It is to be understood thatwhen the engine is started under normal temperatures the fuel will be in a gaseous. state and will be drawn through the carburetor in this state. It is intended that the fuel shall be in a liquid state when the engine has reached. its operating temperature. It will be evident that since the bellows 54 is partially filled with propane that the pressure exerted by the fuel within the bellows will vary in direct relation to the fluid surrounding it. This will be due to the change of the propane from its liquid state to a gaseous state, at which time an increased volume of fluid will prevail within the bellows 64 tending to move the valve stem 6| upwardly and to lift the valve 58 from its seat. It is to be pointed out that as soon as the prevailing temperature drops to a point where the propane condenses the valve 56 will close. This drop in temperature will be produced as the engine speed accelerates and will cause the fuel passing through the carburetor to change to liquid phase, and the fuel which is sealed within the bellows will also condense. This last action will of course relieve the pressure exerted by the bellows and tending to lift the valve 55 from its seat. This compensates forthe conditions created within the carburetor as produced by variation in the physical state of the propane fuel. It will be evident that the pressure of the gaseous fuel passing inwardly through the supply pipe M to the chamber l8 within the bowl l6 will act against the diaphragm 48, and that pressure of fluid passing through valve port 54 will oppose the downward movement of the diaphragm 48 and will be equal to the pressure of the fluid passing through the passageway through valve seat 22. Since the pressures are balanced on both sides of diaphragm 48 valve 24 will be held open by spring 59, allowing gaseous fuel to flow through passageway 96 at full inlet pressure, thereby compensating for the changes in the physical state of the fuel passing through the carburetor.

During the'initial stage of starting the engine,

as previously discussed, it is to be understood that atmospheric air pressure acting upon the diaphragm 89 through the duct 9| will tend to open the valve 83. However, the springs 18 and 86 will act to close this valve. As suction increases in the suction pipe I4 a negative pressure will be imposed upon the upper face of the diaphragm 89 through the duct 94, and this will tend to lift the diaphragm 89 and to move the valve 83 from its seat. Fuel from the intake pipe M will then bypass the entire carburetor structure through ducts 6'! and 68 and thence through the valve opening 8| to the chamber 93, after which it will be drawn directly into the suction line through the passageway 94. This will supply an initially greater volume of fuel to the engine when start ing and might be considered as producing an automatic priming action. When, however, the

suction increases the diaphragm 89 will be lifted further,lifting cup 13, so that the valve 84 will close against the valve seat element and will prevent afurther priming action.

While the foregoing priming action is taking place it will be understood that fuel will be drawn directly from the induction pipe M to the eduction pipe l4'through the passageway I! to the chamber |8 in the bowl J6 and thence through the valve seat 28 .to the space above the diaphragm 48, after which it will be drawn through the duct 96 into the eduction or suction pipe l4. The restricted orifice |0| acts to meter the fuel to maintaina. substantially constant volume. As previously explained-it. will be assumed that the pressure, of the incoming fuel is fifteen pounds gauge. Thisfuel pressure will be imposed upon the diaphragm,48,'but the pressure of spring 59 is less than fifteen pounds gauge so that the pressure in chamber 95 will bereduced to a value determined by spring 59 and the suction imposed on lower side of diaphragm 48 through duct 98, maintaining a relatively constant volume of fuel flowing through orifice |0|, regardless of suction in pipe I4. As the engine speed accelerates the suction in pipe I4 increases. This acts to close the valve 84 and impose a negative pressure within the space 32 occurring betweenthe diaphragms 26 and 3|. These diaphragms are maintained normally in their uppermost position by the expansion of spring 39, since the diaphragm 3| is subjected to atmospheric pressure. When the negative pressure within the space 32 overcomes the pressure of spring 39 the atmospheric pressure exerted upon the upper face of the diaphragm 3| will cause the diaphragms 26 and 3| to flex downwardly and will move the valve 23 to an open position with relation to its valve seat 2|. When the valve 23 moves to its open position fuel from the induction pipe I4 will pass through the valve seat 2| into the space 25 beneath the diaphragm 26 and will then be drawn through the restricted orifice I08 and the duct 44 to the suction pipe M. It will be understood that when the valve 23 moves to its open position immediately a portion of the fuel pressure is imposed upon the under face of diaphragm 26 and will tend to move the diaphragm upwardly and close the valve 23. However, the pressure area of the upper diaphragm 3| is greater than that of the diaphragm26 and will oppose the closing action of the valve, regulating the pressure in chamber 25 to a value determined by the suction in space 32. The spring 39 will act as an intermediate variable factor between the two diaphragms in addition to their pressure area differences and will insure that a suction is built up in the line M. The volume of fuel drawn to the engine through the carburetor |5 will be increased proportionately to the increase in suction, to maintain a relatively constant ratio of the fuel to the airpassing into the engine. This action is more particularly indicated in the graph here disclosed-as Fig. 2, where it willbe seen that while the suction-airflow varies somewhat from an absolute progressive ratio, and that the suctionfuel-flow varies somewhat from an absolute progressive ratio that the mean factors indicated by these two curves demonstrate that in the present device the fuel quantity flow progresses in substantially direct proportion to the airflow.

It will thus be seen that the means here disclosed provides a simple and effective auxiliary equipment for initially starting and maintaining engines started at idling speeds by the use of fuel having the character of propane, and which fuel is always delivered under pressure, the said apparatus acting to increase the volumetricflow of fuel through thecarburetorin'direct proportion to engine suction increase.

While we have shown the preferred means of practising our invention, it is to beunderstood that various changes in the combination, construction and arrangement of partsof the appa- I ratusmay be made by those skilled in the art without departing from the spirit of our inven tionas claimed.

vHaving thus described our invention, whatwe claim and desire to secure by Letters Patent is:

l. A fuel control unit, comprising a housing, an induction pipe connected at one side thereof through which fuel under pressure is delivered, an eduction connection between the housing and the engine, a priming fuel path of travel within the fuel housing from the induction tov the eductionpipes, a normal feed path of travel through the. housing from the induction to the eduction pipes, a pressure regulating valve disposed in the priming path of fuel travel, a feed valve initially closed and disposedin the. normal feed path of fuel travel, fluid responsive. means responsive to increased engine suction tending to close the pressure regulating valve, andfluid responsive means responsive to increased engine suction tending to open the feed valve.

2. The structure of claim 1 including spring means tendingto hold the feed valve in a closed position.

3. The structure of claim 1 including spring means tending to hold the feed valve in a closed position in opposition to atmospheric pressure tending to open said valve.

4. The structure of claim 1 including means between said eduction. connection and the fluid responsive means, whereby a substantially constant pressure drop will be maintained between the fluid responsive means and the engine'suction asthe engine speedaccelerates, and which fluid responsive means'is associated with the pressure regulating valve.

5. In combination with a source of fuel under I pressure, which fuel is characterized as being in a gaseous state at normal temperatures and in a liquid state at lower temperatures connected with the intake. manifold of an internal combustion engine; a control unit including a housing, an induction passageway into said housing communicating with the supp y of fuel under pressure, an eduction passageway from said housing connected with the intake manifold .of the engine, a normal feed passageway to establish communication between the induction and eduction passageways, a priming feed passageway establishing communication between the induction and.

eduction passageways, a main valve in the normal feed passageway normally closed. apressure reg ulating valve in the priming feed passageway normally opened, means yieldably opposing opening the main valve, means yieldably holding the pressure regulating valve open, fluid responsive means acted. upon by engine suction tending to move the main va-lve therein to a full open position, fluid responsive means simultaneously sub- Jected to fuel pressure and engine suction in the priming feed. passageway tending to move the pressure regulating valve to maintain a constant volume flow .of fuel through the priming feed passageway irrespective of engine speed.

6.v The structure of claim 5 including an auxiliary priming passageway leading from the induction side of the housing to the eduction side thereof, a priming valve therein, means acting yieldably to-move said valve to a closed position, and fluid responsive means acting under negative pressurefrom the eduction side of the structure to move the valve to its opened posi tion during a predetermined low negative pressure range and to subsequently close said valve after engine suction increases beyond said negative pressure range.

7. In combination with a source of fuel under pressure, which is characterized as being in a gaseous. state at normal temperatures and in a liquid'state at lower temperatures, a regulating structure having aninduction pipe attached to thesource of fuel supply and an eduction pipe attached to the suction line of an engine, said structureincluding a housing, a fuel flow passageway therethrough from the induction to the eduction pipes, a valve interposed at a point in the length thereof for controlling flow of fluid theret'hrough, a passageway from the induction to the eduction lines leading around the valve, achamber carrying a quantity of volatile liquid interposed in the path of travel of the fuel through said last named passageway, and means operatively associated therewith whereby expansion and contraction of the volatile liquid within the chamber will vary the effective opening.

8. A device for controlling the flow of fuel to an internal combustion engine in proportion to the increase in engine suction, which comprises a housing, an induction ipe connected therewith delivering fuel under pressure, an eduction pipe connected therewith and communicating with the engine intake manifold, a conduit within the housing establishing communication between said pipes, a valve within the conduit, said valve being yieldably held in a normally closed position,

and fluid responsive means subjected to the action of fuel drawn from the induction to the eduction pipes and whereby an increase in engine suction win act upon the fluid responsive means tov open said valve in proportion to increase in engine suction..

9. The structure of claim 8 including a priming feed conduit establishing communication between'the induction pipe and the eduction pipe, a pressure regulating valve therein, a spring yieldably holding the valve in a normally opened position, fluid pressure responsive means acted upon simultaneously by engine suction and fuel pressure and tending to maintain a constant volume flow of fuel to the eduction pipe in proportion to increase in engine suction.

HAROLD W. SMITH. DONALD D. PAXTON. 

